The purpose of this proposal is to participate in the design and performance of multiple multicenter (Clinical Research Network, CRN) therapeutic trials for the treatment of patients with sickle cell disease (SCO). We propose two clinical trials to be considered for performance. 1) To compare dacogen (DAC)to hydroxyurea (HU) in their ability to decrease clinical symptoms of sickle cell disease. Although HU is a benefit in symptomatic SCO,a significant proportion of patients continue to encounter problems despite HU therapy. DAC has been shown to markedly increase HbF levels and decrease surrogate clinical markers of disease severity in all treated patients (HU non-responder and/or intolerant patients). The study design is a phaseIII, open lable, randomized trial comparing DAC 0.2mg/kg subcutaneously (sq) versus HU 15mg/kg. These doses will be increased until marrow depression occurs. The primary end-point to be compared between the two arms will be crisis frequency. A sample size of 100 patients per arm will provide 90% power to detect a 33% difference in crisis frequency. The purpose of this proposal is to participate in the design and performance of multiple multicenter therapeutic trials for the treatment of patients with sickle cell disease (SCO). 2) To develop an effective pain treatment plan for patients based upon the types of pain they experience., and evaluate them for genotypic variability in a number of polymorphic genes, such as mu receptor, MDR1 protein, and cytochrome 2D6. We will accomplish this by using a reliable touch screen computerized tool that the patient will use to obtain a comprehensive assessment of a patient's pain and their response to treatment. To determine if there is a genetic basis for treatment variation, we will evaluate patients for genotypic variability using a number of polymorphic genes, such as mu receptor, MDR1 protein, and cytochrome 2D6.